Arthur Brand provided tips to German detectives who made the discovery in a series of co-ordinated raids, capping a long investigation into illegal art trafficking.

Berlin police spokesman Michael Gassen, who confirmed authorities worked with Mr Brand, said 100 tons of art has been loaded on to trucks in the south-western spa town of Bad Duerkheim where they were found in warehouses.

Eight suspects, whose identities have not been released by police, are under investigation on suspicion of dealing in stolen goods and fraud, Mr Gassen said.

Mr Brand, who runs a Dutch agency that helps track the provenance of artworks and advises buyers on the authenticity of works, says he was shocked when he pieced together enough evidence to prove that recent photos of the Thorak horses were not fakes.